ABSTRACT
OBJECTIVE: To investigate the anatomic feature of the posterior hip joint capsule and its distributional difference of collagen fibers and to probe the optimization of the capsulotomy which can reserve the best strength part. METHODS: Ten adult cadaver pelvises (6 males and 4 females, aged 28-64 years) fixed with formalin were used. Ten right hips were used for anatomical experiment of hip joint capsule. The posterior hip joint capsules were divided into 3 sectors (I-III sectors) and 9 parts (I(A-C), II(D-F), III(G-I). The average thickness of each part was measured and the ischiofemorale ligaments were observed. Five capsules selected from ten left hips were used for histological experiment. The content of collagen fibers in sector I and sector II was analyzed by Masson's staining. Two fresh frozen specimens which were voluntary contributions were contrasted with the fixed specimens. The optimal incision line of the posterior capsule was designed and used. RESULTS: The thickness in the posterior hip joint capsule [I(A) (2.30 +/- 0.40), I(B) (4.68 +/- 0.81), I(C) (2.83 +/- 0.69), II(D) (2.80 +/- 0.79), II(E) (4.22 +/- 1.33), II(F) (2.50 +/- 0.54), III(G) (1.57 +/- 0.40), III(H) (2.60 +/- 0.63), III(I) (1.31 +/- 0.28) mm] had no uniformity (P < 0.01). The III(G) part and the III(I) part were thinner than the I(B) part and the II(E) part (P < 0.01). Two weaker parts located at obturator externus sector (sector III), the ischiofemorale ligament trunk went through two thicker parts (I(B) and II(E)). The distribution of the collagen fibers in sector I and sector II(I(A) 20.34% +/- 5.14%, I(B) 48.79% +/- 12.67%, I(C) 19.87% +/- 5.21%, II(D) 17.57% +/- 3.56%, II(E) 46.76% +/- 11.47%, II(F) 28.65% +/- 15.79%) had no uniformity (P < 0.01). The content of collagen fibers in I(B) part and II(E) part were more than that of other parts (P < 0.01). There were no statistically significant difference in the distribution feature of the thickness and the ischiofemorale ligaments between the fresh frozen specimens and the fixed specimens. The optimal incision line C-A-B-D-E of the posterior capsule was designed and put into clinical application. The remaining capsular flap comprise the most of the ischiofemorale ligament trunk and the part of gluteus minimus. CONCLUSION: Although enhanced posterior soft tissue repair in total hip arthroplasty was investigated deeply and obtained great development, but the postoperative dislocation rate was not eliminated. It is significant for optimizing the capsulotomy to reserve the best strength part of the posterior capsule and to bring into full play the function of the ischiofemorale ligaments.